Overview

Convenience dictates that the broad field of semiconductor lasers be broken up into manageable chunks, and it seems logical to group together those with wavelengths shorter than about 1.1 micrometers ( ?m). Most are based on gallium arsenide, the oldest type of semiconductor laser. Unlike longer-wavelength diode lasers, they have a wide range of applications, including compact-disk players, optical data storage, laser printers, measurement and inspection, laser pointers, and power sources for pumping other lasers. Short-wavelength lasers themselves break into distinct families, as do as some general-purpose lasers.

Short-wavelength laser diode technology has become increasingly versatile as it has matured. Mass-produced milliwatt lasers sell for a few dollars each in large quantities. Monolithic arrays can generate watts of power, and command much higher prices. Some lasers have very high modulation bandwidths for high-speed communications. Others are packaged with focusing optics to meet stringent beam-quality requirements. They employ the family of semiconductor laser structures described in Chap. 18.

New types of lasers have broadened the range of wavelengths beyond those of traditional gallium aluminum arsenide lasers. In late 1990, the shortest wavelength offered was 635 nanometers (nm) in the red, from InGaP/InGaAlP multiple-quantum-well lasers on GaAs substrates. Only one company offered that wavelength, but more were expected to follow.

At longer wavelengths, developers have made strained-layer InGaAs lasers (see Chap. 18) emitting at 980 nm. That wavelength had been sought for pumping erbium-doped fiber amplifiers (see Chap. 26) but had not been available because it was in the lattice-...